FIG. 12 shows an example of conventional LED module (see Patent Document 1, for example). In the LED module X shown in FIG. 12, an LED unit 92 is mounted at the center on an obverse surface of a substrate 91 by using at bonding material, not shown. The substrate 91 is an insulating substrate made of a ceramic material such as alumina or alumina nitride. The LED unit 92 is connected to leads 94 and 95 by wires 93. The LED module X further includes a resin cover 96 made of a transparent epoxy resin and covering the LED unit 92 and the wires 93. For instance, the LED unit 92 is made transparent.
In the LED module X, the obverse surface of the substrate 91 is made white so that light traveling through the reverse surface of the LED unit 92 toward the obverse surface of the substrate 91 is reflected. This assures that light emitted from the LED unit 92 is efficiently utilized.
However, when the LED unit 32 is directly mounted on the substrate 91, heat generated during light emission of the LED unit 92 is not easily dissipated as compared with the case where the LED unit 92 is mounted on a wiring pattern made of a metal, for example. On the other hand, although a wiring pattern made of a metal is an excellent heat dissipator, its surface may change to a dark color as time elapses. Such color change hinders efficient utilization of light from the LED unit 92.